Rihanna enlisted the help of some charitable famous friends on Thursday for her first annual Diamond Ball, with Brad Pitt, Jimmy Kimmel, Kim Kardashian and Salma Hayak all stepping out to show their support.

"When I first started putting this together, I just wanted it to be sincere and about the foundation and about giving back," Rihanna told ET's Sophie Schillaci on the red carpet at The Vineyard in Beverly Hills. "But to see people wanting to jump in and support it, I can't tell you how happy I am."

The black-tie event raised funds for Rih's Clara Lionel Foundation, named for her grandparents, which aims to improve the quality of life for global communities in the areas of health, education, arts and culture. Among the foundation's triumphs thus far is the Clara Brathwaite Center for Oncology in Nuclear Medicine at the Queen Elizabeth Hospital in Barbados, named in 2012 for Rihanna's late grandmother.

Wearing a stunning Zac Posen gown and Chopard jewels, Rihanna dazzled on the red carpet but shared the spotlight with her family. Grandpa Bravo (aka Lionel) was beaming by her side.

Among the night’s highlights were performances from Big Sean and Rihanna herself. The superstar enlisted Pitt to make an on-stage appearance introducing her set (which, sadly, did not include new material).

"He's the one that loves charity," Rihanna said of Pitt. "When I reached out to him, he was more than happy to do it. It's just a matter of giving back."